I've used it a few years back. It works as advertised but it's nothing special. Yes, you have to pay for the software and you'll have to pay monthly if you want the high-quality data (which you do need if testing lower timeframes). You could just pay for 1 month, download all the data you need, and then cancel the sub. It won't give you any new data after your sub ends, but you'll still retain everything you have if it's saved to your hard drive.

Really though I would recommend soft4fx over Forex Tester. It uses dukascopy's data so there's no monthly data fee. It's built into MT4 so there's less of a learning curve. Plus there's a free cracked version that's widely circulated among most trading groups at this point. I can pm you the download link if you want it. Or if you choose to buy it from the devs, I think it's still cheaper than Forex Tester.