If it's anything like the Rivera-era Princeton Reverb II, that I stupidly got rid of in 1990 (I keep an eye out for them on evilBay, hoping to get another one), I'd say pretty good. Nice cleans. Use the boost function, with the pull-boosts on the mid, treble, and bass controls, and and it has some good overdrive, without the fizz, the evil (red knob) Twin can have. Not super high gain, but still pretty good (sort of early JCM800, or Mesa Maverick [another amp I stupidly sold], depending upon how you set it up). Run a clean boost into them, while in the boost mode, and watch them scream! I remember one time, running a Chandler Tube Driver into my Princeton Reverb II, while it was in the Boost mode, and going nuts before a rehearsal (I was in a pop covers band at the time, so there was no way I could do it during band time) blasting away on Soundgarden's "Ugly Truth", complete with the feedback effects.
The Rivera Era Twin ought to sound pretty similar, but possibly a little cleaner, due to Twins characteristically having a fair amount of clean headroom. The only problem you're going to have, is that Rivera-era Fenders go for some serious bucks nowadays. That's why I've yet to get another Princeton Reverb II. At 800-$900 for one (I paid like $350 for mine used, back in late 1989), all I could say was, "nope!, not right now!" Rivera-era Twins go for a quite a bit more. But if you have a good lead on one at a good price, it's worth snapping up. IMO, besides the overdrive, they take pedals very well. The only hassle is the footswitch for boost mode, and reverb. They've always been kind of hard to find (although you can access both functions from the front panel). But, you could always do with out it, be patient, wait, and get one off of eBay, or mod another switch to do the job for you.