I've used them, but don't have one. It's a nice option. I've often thought of getting one. The big advantage of an iso cab over a load box with speaker simulation is that you can get the tone of the speaker breaking up, and control that a lot more than with most load boxes. A speaker IR is, after all, a static sample of that speaker, at such-and-such volume, etc. It's going to vary a lot more with a real speaker. The only drawback is that there's less "air" around the note due to the lack of space in the enclosure. OIf course, that can be addressed to a degree with reverb, especially in a DAW. The UA OX does a great job with emulating speaker load, however, because it uses algorithms instead of IRs. I'm not pushing this solution; I don't have one of those either, because my 'solution' is to just record freakin' loud and call it a day. But there may come a time when my neighbors won't be hard-of-hearing old people, and I get nasty feedback. When that happens, I'll get either an iso cab or a UA OX.