～たはいいが says you did something, and that part was fine, but it has left you with a problem: "I did X, all well and good, but…". The verb is in the た-form, and the second half names the trouble.
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I bought a new car, which was all well and good, but I don't have a parking spot.
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I changed jobs, which was fine and all, but now I regret it because my previous job was better.
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I quit my job, which was all well and good, but I can't seem to find the next one.
The tone is rueful or wry. Often the speaker acted without thinking it through and is now stuck with the result.
たはいいが or たものの
is a plain "although I did X". たはいいが first grants that doing X was fine, even a good move, and then turns to the problem, so it carries more irony.
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Although I bought a Japanese book, it was too difficult to read.
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I got a dog, which was fine, but the daily walks are exhausting.
Other endings
The ending after いい follows the register. is the conversational form, the written one, and puts the "fine" in the past as well.
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I made the food, which was fine, but nobody ate it.
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I went independent, which was all well and good, but my income is completely unstable.
Lingaku