Before you scoff at the title, consider this:
1) Today's PC's are a lot more powerful than when Minecraft versions 1.4.7 thru 1.7.10 were released.
2) Java 8 does a much better job at Garbage Collection than previous versions used to program Minecraft Java version. More ram for the game.
3) Light weight Java GL (LWJGL) the primary graphics engine is much improved. The graphics errors are still there in these older versions of Minecraft, but they do not stay as long.
4) Feed The Beast modpacks from MC 1.4.7 through MC 1.7.10 have a very well established wiki documentation. Especially with FTB Ultimate modpack mods.
All this will not make the bugs in some of those older mods or Minecraft go away, but they are more tolerable.
Previous lag issues literally disappear, I can play for long hours without the need for any kind of resetting the game.
FTB ultimate experiences:
XYcraft was still too buggy to use. So I disabled it. If you decide to disable the mod after starting a world, you will find a lot of gaps in the stone you excavate, making it look like the mod might have over written or at least taken up space where more valuable ores of your preference could have been.
if you pursue large quantities of emeralds, I was only finding them in Vanilla Biomes, so ExtraBiomesXL reduces the chances of Vanilla biomes. so disabling this mod may be an option. ( I think snowy jungles are a controversy anyway)
Redpower 2 is still the most powerful and diverse mod (IMO) very created, however, be reminded of the Timer logic chip bug. Do Not hold any place-able item while trying to access the timer setting menu. This causes a totally game crash back to your desktop.
Thaumcraft has some very annoying Wisps, which seem to only be killed by pursuing the mod enough to get one of those wands to shoot it out of the sky.
Greg-Tech addon to IC2 may or may not be a preference. This mod attempts to balance most of the recipes and functions in the other mods. Disabling this addon mod makes all that disappear.
1) Today's PC's are a lot more powerful than when Minecraft versions 1.4.7 thru 1.7.10 were released.
2) Java 8 does a much better job at Garbage Collection than previous versions used to program Minecraft Java version. More ram for the game.
3) Light weight Java GL (LWJGL) the primary graphics engine is much improved. The graphics errors are still there in these older versions of Minecraft, but they do not stay as long.
4) Feed The Beast modpacks from MC 1.4.7 through MC 1.7.10 have a very well established wiki documentation. Especially with FTB Ultimate modpack mods.
All this will not make the bugs in some of those older mods or Minecraft go away, but they are more tolerable.
Previous lag issues literally disappear, I can play for long hours without the need for any kind of resetting the game.
FTB ultimate experiences:
XYcraft was still too buggy to use. So I disabled it. If you decide to disable the mod after starting a world, you will find a lot of gaps in the stone you excavate, making it look like the mod might have over written or at least taken up space where more valuable ores of your preference could have been.
if you pursue large quantities of emeralds, I was only finding them in Vanilla Biomes, so ExtraBiomesXL reduces the chances of Vanilla biomes. so disabling this mod may be an option. ( I think snowy jungles are a controversy anyway)
Redpower 2 is still the most powerful and diverse mod (IMO) very created, however, be reminded of the Timer logic chip bug. Do Not hold any place-able item while trying to access the timer setting menu. This causes a totally game crash back to your desktop.
Thaumcraft has some very annoying Wisps, which seem to only be killed by pursuing the mod enough to get one of those wands to shoot it out of the sky.
Greg-Tech addon to IC2 may or may not be a preference. This mod attempts to balance most of the recipes and functions in the other mods. Disabling this addon mod makes all that disappear.
Just wanted to add my own experience to yours - for me, there's no going back, sadly. If that feeling is still out there somewhere, it will be found in the modern modpacks. I try to keep the faith I'll find it someday again, but I'm also a pessimist. At least I learned those good memories of v1.4.7 days are better left as just that - good memories. 