From what I've always been able to gather, management expects their sysadmins to be 'up' on new technologies, software, processes etc. I also tend to agree but like the title says, is tinkering or experimenting with equipment or software considered to be a regular part of the job. Not just something you do on your own time.
Basically, if the ceo of the company were to walk in to your office, and you are seeing what it's like to install/configure/manage a new technology, is it a reasonable reply to the "what are you doing?" to say "playing with X_TECHNOLOGY [and insert, maybe, a reason why you're considering it]" ?
edit> Very informative answers so far, thank you very much. I'd also like to ask if there is commonly a budget for such ventures (I imagine, usually for testing potential hardware implementations) and if so, how much as a percentage of the IT budget is it usally?