I started to run it in 5th, but I did not get very far. I ended up with just converting the first book (The Iron Circle). I did not find any other conversion that I could use.
I was not sure what level would be appropriate for each part. My original plan was to run Reavers of Harkenwold, Cairn of the Winter King (Monster Vault adventure), and finish the path with Maddness At Gardmore Abbey. Since my players still like minatures, that gave me an adventure path with maps and monster counters. I figured I could go from level 2 to 8 in the adventures. I ended up scrapping the campaign and switching to CoS.
I pretty much just spent my time finding comparable monsters to substitute for the 4E ones.
Here's what I ended up with:
4 Players level 2 (we had a 'get to know your character' intro adventure)
Encounter E1 (200xp)
4 Bandits
2 Wolves
Encounter E2 (280xp)
2 Bandits
2 Scounts
3 commoners
Encounter E3 (350xp)
1 Acolyte
4 Bandits
1 Death Dog (instead of Iron Defender)
Encounter E4 (290xp)
1 Acolyte
3 Bandits
4 Commoners
1 Worg (instead of a drake)
Encounter T1 (275xp)
4 Bullywug
3 Stirges
Encounter t2
Did not run this one
Needs a caster bullywug and minions
Encounter t3
did not run
needs bullywug champion
Encounter D2 (200xp)
4 Tree Spiders
Encounter D3 (650xp)
1 Goblin Boss
5 Goblin
2 Worg (instead of drakes)
Encounter D4 (2850xp) very tough fight. It is still ranked as deadly if the party is level 4. I ended up making it an RP encounter where they had to trick the mage and trap him in his lair.
1 Mage (can give him skeleton immunities and vulnerabilities)
2 skeletons
1 Ettercap