Any opinions on VTL mono-blocs MB450, etc ?

I think both are very nice amps. I have the VTL 450s and a good friend has the VT200 (not the MkII I believe). I like my VTLs very much. They make my music sounds fabulous. The highest complement I can pay them is that while I have envisaged upgrades to various parts of my system (even the rack) from time to time, I have not once thought of upgrading the amps.

As to your questions...
1) Reliability: I have had my VTL MB 450 Signature monblocks for 14mos (bought used at the time) and they have had no problems whatsoever (knock on wood). I have not heard any dealers complaining about VTLs, even if they have competing products to sell (such as Jadis). Reliability seems to have been a bugbear for some in the past (see the archives here or over at audioasylum. It is probably worth asking your VTL dealer about this as well.
2) Weight: they are heavy - 35kg/80lbs apiece - and the weight is somewhat awkwardly placed within the chassis. They are not for people who like moving stuff around every week.
3) Heat: they put out some heat but it's not overbearing.
Notes on #2 and #3: The VT200 is heavy (I'd put it at ~50kg/120lb give or take) and puts out quite a bit of heat.

I agree with Mejames in that when/if you demo the VTL 450s, it is imperative to demo them in triode. While tetrode is very, very good, triode can be magic. I find the VT200 sounds somewhat "hard" when compared to the 450s in triode mode. If you don't need the 400-500 watts that the VTL 450s can provide in tetrode, you might also try the MB 250s, which offer 200WPC in triode only.

Another high-power tube amp you might consider in the same price range would be the Wolcott Presence 220 monoblocks (though I've never heard the Wolcotts, whenever I see comments about comparisons between the VTLs and the Wolcotts, the VTLs always seem to come out second best). I would also recommend trying the Counterpoint Natural Progression series (even though they are less tube amps than hybrid amps). I was very impressed with the monoblocks.

Thanks for all the feedback here.....also has anyone owned/listened to C-J Premier 12's? Would they be "better" than the ARC VT100? They are about the same price as the VTL MB450's, but have *only* 4 6550's each (as opposed to 8 6550's each in the VTL's). I'm asking because I always had the Premier 12's on my list of possible, someday, ultimate amps along with VTL's.

Steve

hello Steveaudio I was loaned premier 12 amplifiers for approximately 3 months before they simply are not in the same league as the 450 signatures especially the bass.
Audition the 450 signatures somewhere you will see.
in addition to my previous post above I have had absolutely no reliability problems with my 450's since I purchased them. They run cooler than most other tube amplifiers because of lower bias which increases tube life considerably a good idea for saving $. I actually prefer the 450's to my recently sold Wolcott presence 220 amplifiers which just sounded to thin and lacking some harmonic richness in the mid range compared to the 450 especially in triode mode.
Wolcott amplifiers have considerable heat output much warmer than the 450's

You might also consider Air Tight ATM3 mono blocks. I have them matched to Genesis 500 speakers. A terrific value for the performance vs. price.
I have not compared them to the VTL 450 amps, and would welcome feedback from anyone who has compared these amps.

from my auditioning the CJ are a lot more tubey than ACR or VTL. As mentioned above the triode mode in the VTL is killer in small group stuff, acoustic music and vocals especially. ARC doesn't have that option. If you want a bit more thump then flip the switch and go tetrode. My 185s have been spending most of the time in tetrode. Compared these with the ARC and think the VTL has a more open natural sound. VTL are also monos while the arc is a single chassis so there are room and set up considerations. The monos do throw off some heat, good in the winter when i do the most listening, less so in the summer. I wouldn't really complaing about owning either the ARC or the VTL but prefer the VTL. THe 185s are plenty for me and the only other consideration for me may be the 250 triodes. The 450s and bigger would only be of use for difficult speakers or a huge room IMHO. As to problems: have an intermittant hum in one of mine that goes away as soon as you toggle the power switch on and off. been that way for 3 yrs, ain't bad wnough to be without them to get it fixed. Was playing them way to loud the other day and blew a B+ fuse when i turned on the vacuum (could barely hear it)....time for dedicated lines i would guess.