I have seven domains hosted in 1planhost.com for more than one year. I always find somebody ask for Windows 2003 hosting suggestions. Here are my personal review. You can test my web sites: jt-dev.net, jt-demo.net, ..., etxahec.org, etrap.org, ...
Pros:
1) More than 7 years hosting experiences and over 5000 domains hosted with them.
2) Experienced some down time with their old server (Win2000). But nerver have down time with their new server (Win2003).
3) They have several technical support staff. The response is always fast.
4) The plan is affordable (750MB/45GB/$8.25).
5) I never had problems with their HELM control panel. HELM is much stable than Pleask 6.5.2.
Cons:
1) The plan is best for ASP.NET hosting that don't need database (SQL2000: 50MB/$35/Yr. ). My Web site only need 10MB Web space but 100MB SQL space. So I need to pay $99/Yr + $75/yr = $174.00/Yr.
2) Cannot support Frontpage site search in their server.
3) Experienced some session timeout error and the SQL Enterprise manager cannot enter edit mode sometimes. It took almost two months for them to fix these two problems. Right now all the problems have been fixed.
4) Don't have multiple domains hosting plan.
5) HELM has less features than Plesk. For example, you always need to create a ticket to change the file permission. But their support staff always do it for you very quick.
I also tried amzhost.com, exovian.com and ddihosting.com. They have the better plan than 1planhost.com for SQL 2000 hosting. But the server of amzhost.com is not stable and secure. exovian.com has bad support. ddihosting.com is too new to the hosting market.
Conclusion: 1planhost.com is the best affordable ASP.NET hosting provider right now.