I've been running HM2 since April, when it was still in Alpha testing. Other than NotesCaddy, which is still buggy as hell IMO and why I keep it disabled, HM2 runs perfectly fine for me. Until June I ran HM1 in parallel with HM2, but in June I switched completely to HM2 and would never consider going back.
I pretty much live in the HM support forums too, and the stuff about releasing early with tons of stuff not working is mostly BS. I've been deeply involved with alpha/beta testing. Testers were clamoring for release for months beforehand, but HM kept postponing the release to get things "right." It was quite complete and stable by then, but then just at release they rolled out a massive update with a TON of new features and fixes that really didn't get a long enough test cycle. So yeah, GA had some rough edges, but they were releasing 2-3 updates a week to address them and quickly got the worst bugs under control.
It's been quite stable now for some time for a lot of us. Most people having performance problems are due to NotesCaddy, which is included with HM2 now but not developed by the HM2 development team, it's a 3rd party author's product who has his own support area on their forum. I recommend you turn NC off completely until it becomes fully baked. I have no performance issues with multi-tabling and NC disabled.
There are thousands of satisfied HM2 customers, only the most vocal 100 or so with major issues are complaining loudly and saying it's "unusable." And that's their right of course as paying customers, but to suggest that it's not usable for anyone is straight up BS. You've got 2 people right here in this thread so far saying we're running it without major issues. If you've lived in their forums as much as I have, I think you'd know that people were complaining about HM1 problems and bugs right up until HM2 was released, and HM1 has had almost 4 years to get it right. HM2 is a much more ambitious project and a complete re-write of HM1, so it's not surprising what with all the myriad of user system variables out there that they will have rough edges starting out. As someone in the software development field, this is totally not surprising, and I've seen a LOT worse rollouts of major software releases than this.
As to the licensing, they have repeatedly stated that HM2 users can switch back and forth between HM1 and HM2 licenses by just emailing support. You cannot activate both at the same time, but you can choose which one you want to run.
JoeBob, I expect your problem was NotesCaddy as well. Same thing happened to mine right around release, and I looked and noticed NC had been enabled. Turned it back off and things were fixed. The NC author (which as I said is not the HM people) has supposedly released a few bug fixes to address the problem, but from what I'm hearing NC is still not ready for heavy volume yet.