I have been on Samp since v8.
I would have jumped on the upgrade to ProX v12 when it came out, except that with the new pricing scheme, prior owners of the "Pro" version are funneled the "lower" upgrade track, the same as prior "Classic" users. This stings a bit.
Now, I am considering the upgrade because it 64bits and I can use all my computer's memory, but I really dont have any usability or feature complaints with v11 Pro, so I am staying with v11 for now.
For any "home" users interested in Samp, let me give my impressions of the software.
Prior to Samp, I was a CWPA/Sonar user from the mid 90s, and I have auditioned most of the major sequencers except Logic and Nuendo through about 2005. So I don't really have knowledge of what is available now (except for reaper). But 7-ish years ago, Samp was leaps and bounds ahead of the other software in sound quality.
Also the user interface had a very fluid feel to it and the audio engine/transport is very responsive. You can drag the transport, set up markers, loops, do almost everything in real time without freezing or stuttering. This is an intangible quality, but makes it feel more like a hardware device.
Samplitude Pro cost 1K prior to ProX, and while this was very expensive up front, the included plug-ins were much higher quality than what I was using. Even simple things like the mixer EQ sounded better. Back then it was either UAD or Waves for high end consumer plugins, and those were both expensive (and look where they are now) Today with multi cores and the competitive plug-in marketplace, one may be able to supplement their plug-in arsenal with affordable native alternatives, but as a baseline, the Samp included FX are still excellent, imo.
The complexity of the software is good/bad depending on your ability and needs. Professionally, i am a software engineer and am used to technical complexity, but that said, I spend most of my recreation time playing/practicing music, and Samplitude is still a handful. (Every other sequencer I have used, I feel as if I "know" the software in a week or so.) I dont think this is because of problems in samp design, just the level of power/complexity. There are buttons/widgets for everything which will save having to go into menus, and contributes to its "hardware" feel. But make no mistake, it is complex.
If I worked with the software every week I would gain more proficency, but as now I just stick with basic things, and occasionally delve into deeper functions. I have never felt it could not do something. Its clear it was developed for professionals. I think it has a very "German" feel to it.
Because it has many professional users, the forums have a high degree of knowledge and quick turnaround answer on questions. (Most of the other forums are full of kids making techno with "warez", none of that nonsense in the samp forum.) I have emailed tech support before and gotten quick turnaround from Germany on a fairly complicated issue, and have also talked with Tim Dolbear who has offered great phone support. Its amazing to have direct access to someone with his knowledge, if needed. I think support for Samp is great, but because it is not as mainstream as say Cubase, you wont get constant validation from the music community and advertizers. Its a small, but talented family of users. (Fortunately, Samp/Sequoia are the big brother to the Music Maker program and Magix is long established so there is no danger of Samp disappearing, imo.)
That said, there are other tools that do things "better" than samp. I use Sibelius for scoring rewired to Samp. (Although Samps scoring has evolved considerably over the past 5 years.) I am also considering checking out the latest version of Ableton for composition (again, rewired to samp).
In summary, I would say it has a very professional feel, highest quality sound, but it might be overwhelming for typical home recordists who are primarily musicians and dont have alot of time to devote to learning the program.