I don't think it will be too bad. I've used other home replacements aHome, Pandahome, Openhome, etc... They all had pros and cons but ultimately they didn't offer any thing different than Sense; so I ultimately went back to Sense. I experienced some force closes but I don't think they were caused by HTC Sense. As I understand it they're apps and as such they don't interact with Sense at all.
TAT Home is very intriguing and I'm really looking forward to it. It turns out the phone on the video is a GSM Hero and it looked really responsive. As for SPB Mobileshell I'm on the fence. I used it during my WinMo days on my Treo Pro and Touch Pro and it lagged horribly. In the preview video here
http://pocketnow.com/tech-news/mwc-v...-50-on-android it looks to lag on the N1. Maybe because it's not a final build so hopefully the lag will be remedied before launch.