Even though some people believe software plugins can't compete in the same league with good hardware units, I'll throw out a few suggestions of plugin verbs that have worked well for me. NOTE: I have found that user presets in most plugins are not useful at all, and that tweaking is nessecary to achieve a workable sound.
Sonic Timeworks ReverbX is excellent in my opinion. Plenty of parameter adjustments and a very open sound. The Timeworks 4080L is also very good, but has fewer adjustments, and is a little less flexible.
Both verbs offered by Waves are also very good.
The Renaissance Reverb is similar in sound to ReverbX, but with even more tweaks available.
Waves Trueverb is great for simulating rooms/distances.
The Ultrafunk reverb is also another favorite of mine...with the ability to control how 'stereo' the verb is (can be very handy for creating space, or closing things off).
If you have the processor power, then Sonic Foundry's Acoustic Mirror is another good choice, because it has the ablility to simulate 'real' spaces, and can be used for special effects as well.
Rumor has it that a plugin similar to Acoustic Mirror, called Altiverb (
http://www.audioease.com/Pages/Altiverb/AltiverbMain.html) is going to be available soon for the PC, and from the examples I've heard, it's even better than Acoustic Mirror.
Whatever plugin(s) you choose, the most important thing to consider is how to best utilize and tweak it. Play with the parameter adjustments, and get the verb to fit the groove of the music, and be careful when using more than one verb at once, as incorrect adjustments will make them fight each other (resulting in a wishy washy sound, or other funky artifacts). In many cases, I've only used one reverb in a song, because it helps glue all the tracks together.
Even though it's probably true that software plugins (at this moment in time) are probably not as good as their hardware counterparts, they can be very usable if you get to know them inside and out, and tweak them appropriately.
