I signed up to XenSmart just over three weeks ago to the 512MB plan (£16pm, but cheaper as found in the offers forum).
Despite no HyperVM usage for obvious reasons, setup was still quick, and all was ready in a couple of hours. The VPS has been up constantly in that time, and a third party monitor has experienced no problem (that I know of) connecting.
I had one query that couldn't be answered from their website and this was responded to within a couple of hours also.
I have been connected to the VPS for extended periods, setting various things up and compiling some programmes, and never noticed any slowing of the server. Of four providers used up to now, this VPS has stayed up the longest and had the least (no) problems.
There is, however, no restore or remote reboot or other similar functionality at this time because of the lack of HyperVM, but support by email seems to be pretty quick anyway. Also they are very clear this is the unmanaged side of their business, so you need to know what you are doing because they are under no obligation to provide general help.