I'm thinking about getting a second-hand Mac...

Internet Explorer ain’t gonna happen. And good riddance, you’ll never look back.

OSX is a rock. Get at least 1GB of RAM. I had a friend who installed Leopard on an 800mhz G4 eMac and he said it ran surprisingly fine. I think anything you get for $800 should have much better specs.

I have a iMac with a 1.83 GHz Core 2 Duo with 2 GB of RAM.

I would say my iMac feels a little slower when it runs OS X compared to XP with BootCamp. But it is just the UI that doesn’t feel like it runs as quickly. Things like encoding video work out about the same.

Overall, my work flow is smoother on OS X. I get more done in less time with OS X. And I don’t worry about spyware and viruses.

I really don’t have any concerns about the speed of the machine and I do just about the same things as you. I would take the plunge. And if you hate it you can probably sell it for about what you paid for it.

And buy as much RAM as you can.. OS X gobbles up RAM.

I have a Mac Mini (1.66GHz Intel Core Duo w/ 2GB SDRAM) running OS 10.5 and it’s perfect for any needs it seems you’d have. I suspect you’ll find that you’ll choose different applications once you make the switch (Safari instead of Opera, Adium over MSN Messenger, Coda or Rapidweaver over Dreamweaver). You can get a used Mac Mini for < $800. As mentioned, max out the RAM.

Do get the RAM, but don’t blame the need for it on OS X itself (cf John’s last line): MS Office, Photoshop and a browser will eat up a lot of RAM, especially over time (I think they do leak memory). And it appears that Mac users have a habit of never quitting their programmes, as they just put their Mac to sleep and close windows, not the program itself; so it never really gets cleared. 2GB should be fine though.
Otherwise, they should run things fine, even when your CPU is not the fastest.

I second Evert’s recommendation. You ought to be able to get a fairly recent Mac mini (b.y.o. keyboard, monitor and mouse!) for less than $800 AUD. But, load it up with RAM, as much as it will take. Seriously. I use Macs every day for work and play and I consider 2GB the minimum usable amount. Unfortunately, that’s the max in the mini. If you plan to do anything really resource intensive (like video editing), you probably want a more capable machine, like an iMac with 4GB of RAM and a real video card.

@ evert – I agree that 2 gigs should be fine, although memory management are really a thing of the past. I work in Illustrator, Photoshop, AfterEffects, FinalCutpro, Itunes, Adium, Mail and Firefoxe 8hours a day everyday in my job and don’t have troubles.

That being said, ram is so cheap it is really the cheapest thing you can do to give your computer’s CPU the best chance at running unencombered.

@ segdeha – “the max in the mini” I enjoyed that

You can get a decent Core 2 Duo Mini for about $500 on Apple’s returbished equipment page (hit http://store.apple.com and look for the “Special Deals” button). Spend another $150 on replacing the RAM with 2 1gb DIMMs from NewEgg.com and you’ve got a nice little machine there. I love Apple’s refurbs. They do a nice job on repairs before they go out again, and the odds of them failing twice are incredibly low. You wind up with a reliable Mac for about 20% off retail.

@Bri_L: yes, perhaps it from my experience with just a few programs, but particular Safari & FireFox feel like memory hogs. Other than that, never really had problems. And I’m guessing that it will feel smoother to jonno than Windows, after having gotten used to it.
Jonno, MacBook or iMac probably depend on your portability wishes (and MacBook nicely tucks away of course); but I’ve found a 13” screen rather smallish for all-day work myself.