You can still use the vSphere Client v5.1 and not the Web Client if you wish though the future is Web access to get away from Client apps like many other software companies. I upgraded from v4.1 to v5.1 and though the Web is very different than the client, you can still download the client and use that as in times past which I actually still do on occation since I'm still learning the Web based version.
Regards, CSSMP