No, it is not worth purchasing on your own. I second the opinion that Emedicine is a good free alternative.
To be honest, I barely ever used UpToDate as an intern. If your hospital doesn't provide you with an official subscription to UpToDate, substitute with whatever resource you want. My favorites are:
1) Ask senior resident.
2) A pocket reference or PDA reference.
3) Emedicine.
4) Google.