I purchased and installed an ASUS GT 240 into my Dell E510/5150 because I needed some more graphics performance and I wanted to run Windows 7 AND I didn't want to purchase another desktop. I am totally satisfied with the GT 240 and I haven't even overclocked it. (yet). As one poster commented the complaints seem more geared towards the fact you can get a graphics card with more horsepower so to speak cheaper than the GT 240. However if you are like me and running a OEM style PC (Dell, HP, Gateway etc) you are limited by your power supply wattage. This is what makes the GT 240 worth it to me. My Dell has a 305 watt PSU and other than a NVidia GS 8600(which is discontinued) my choices are very limited for a graphics card upgrade. I assure you that the 240 will handle all of your childrens' learning game and do it beautifully. I'm not a huge gamer, but I like to play occasionally. I run Call of Duty maxed out and it looks beautiful. I play FarCry 2 just about maxed out as well as Fallout 3 and Assassin's Creed maxed out. All of them run and play really nice. I'll give you the specs on my system for comparison - again it's not a new system but I have upgraded some parts.
Original Specs:
Intel Pentium D 820 2.8 Ghz processor
512 MB RAM
ATI Radeon X300SE (128 MB RAM) (PCI-Express))
80 GB Western Digital hard drive
10/100 built in Ethernet
Through smart shopping on NewEgg and eBay I've been able to upgrade the following for less then 320 bucks.
Current specs
Intel Pentium D 940 3.4 Ghz processor
4 GB RAM
Asus GT 240 PCI-Express with 512 MB of DDR5 RAM
750 GB Caviar Black hard drive
500 GB Seagate Barracuda hard drive (7200 rpm)
Dynex Gigabit Ethernet card
I have to tell you that my old Dell runs like never before. I know there are people out there with much much better systems than mine, but I am very happy with what I have and I kid you not when I tell you that it really does fly. Windows 7 Pro 64 bit loads fast, looks great, my games load and great and since the gigabit Ethernet card, I can actually notice the difference in downloading Web pages, files, and uploading files to my server in the cloud.
I know I went overboard and please believe I'm not trying to toot my horn. As I said there are tons of people with much better systems than me. My MAIN point to you was that buying the GT 240 was a very good decision for me, as was upgrading the other components. I won't have to think of purchasing a new desktop for another couple of years, and for that I know that I got my money's worth from these components, and I'm sure my son will love playing Thomas and Friends to his hearts content.
I will also tell you that the brand of GT 240 makes a significant difference as well. I'm very happy with my Asus brand - they are a brand that has earned my trust over the years, but there are other good brands out there, like MSI, XFX etc to consider. I purchased the Asus because I have used their products for over 10 years now. I also like the Asus because it came with a little software app to measure your GPU temp as well for overclocking, and one last huge factor was the 'ginormous' cooling fan that Asus puts on their 240. The larger fan means fewer RPM's to cool the card, which reduces the power drain on your power supply.
I hope you can use some of what I've said to help you make a sound decision. I had similar questions when I was searching. Good luck in your purchase!
Here is the link from Newegg to the card I purchased. while you may be able to find cheaper, Newegg is so reliable I will pay a few dollars more for peace of mind.
http://tinyurl.com/ASUS-GT-240
Robert